8000 Fix --x-initial and --x-assign random stability (#2662) by toddstrader · Pull Request #5958 · verilator/verilator · GitHub
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Fix --x-initial and --x-assign random stability (#2662) #5958

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Merged
merged 21 commits into from
May 16, 2025
Merged

Fix --x-initial and --x-assign random stability (#2662) #5958

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095eefc
x rand test
toddstrader Apr 28, 2025
c2549d1
POC: VL_RAND_RESET PRNG stability
toddstrader Apr 25, 2025
f0005ca
runtime scope hashing -- WIP
toddstrader Apr 30, 2025
63e2e68
split rand reset into scoped and not
toddstrader May 1, 2025
8f740ca
format
toddstrader May 2, 2025
228a7c2
Handle classes
toddstrader May 2, 2025
76806e4
vltmt
toddstrader May 5, 2025
30434fb
VL_MT_SAFE
toddstrader May 5, 2025
fba7ab5
cleanup
toddstrader May 5, 2025
d53da10
remove xtemp initial assign
toddstrader May 5, 2025
31a388a
AstRand::m_reset rip out
toddstrader May 5, 2025
52ba867
fix rand initial
toddstrader May 5, 2025
5ad37ec
use --x-assign for XTEMP reset
toddstrader May 5, 2025
02925b3
this / vlSelf
toddstrader May 5, 2025
c2a5052
fix t_debug_emitv
toddstrader May 5, 2025
df85809
py fix
toddstrader May 5, 2025
cfb74a4
CR
toddstrader May 6, 2025
8d691d5
golden
toddstrader May 6, 2025
4680ade
unsafe
toddstrader May 6, 2025
2189af1
fallthrough
toddstrader May 6, 2025
8efb24b
CR
toddstrader May 16, 2025
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cleanup
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@toddstrader
toddstrader committed May 16, 2025
commit fba7ab56aff6a07eccd0a5696cac8035e517fec0
9 changes: 0 additions & 9 deletions src/V3EmitCFunc.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -24,9 +24,6 @@
#include <string>
#include <vector>

// NOCOMMIT
VL_DEFINE_DEBUG_FUNCTIONS;

// We use a static char array in VL_VALUE_STRING
constexpr int VL_VALUE_STRING_MAX_WIDTH = 8192;

Expand Down Expand Up @@ -674,8 +671,6 @@ void EmitCFunc::emitVarReset(AstVar* varp, bool constructing) {
string EmitCFunc::emitVarResetRecurse(const AstVar* varp, bool constructing,
const string& varNameProtected, AstNodeDType* dtypep,
int depth, const string& suffix) {
UINFO(1, "Var Reset -- " << varp->prettyName() << " -- " << varp->name() << " - "
<< varp->origName() << " -- " << varp << endl);
dtypep = dtypep->skipRefp();
AstBasicDType* const basicp = dtypep->basicp();
// Returns string to do resetting, empty to do nothing (which caller should handle)
Expand Down Expand Up @@ -778,7 +773,6 @@ string EmitCFunc::emitVarResetRecurse(const AstVar* varp, bool constructing,
if (!zeroit) {
emitVarResetScopeHash();
uint64_t salt = std::hash<std::string>{}(varp->prettyName());
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Suggested change
uint64_t salt = std::hash<std::string>{}(varp->prettyName());
const uint64_t salt = std::hash<std::string>{}(varp->prettyName());

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C++ "Hash functions are only required to produce the same result for the same input within a single execution of a program". So use VString functions instead, making a new one if needed.

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That's a bummer.

I dropped a hash function in V3String and also the runtime library. Is there something better to do here? I don't see any hash functions already associated with VString. There is a SHA256 in there, but it speaks about 64B blocks and I don't think that's what we want for this application. There's also V3Hash but that is intrinsically 32b. Also, is there a reasonable way to share code between the compiler and the runtime? I'm not seeing any examples.

UINFO(1, "Var Hash -- " << varp->prettyName() << " -- " << salt << endl);
out += ", ";
out += "__VscopeHash, ";
out += std::to_string(salt);
Expand All @@ -799,10 +793,8 @@ string EmitCFunc::emitVarResetRecurse(const AstVar* varp, bool constructing,
} else {
emitVarResetScopeHash();
uint64_t salt = std::hash<std::string>{}(varp->prettyName());
UINFO(1, "Var Hash -- " << varp->prettyName() << " -- " << salt << endl);
out += " = VL_SCOPED_RAND_RESET_";
out += dtypep->charIQWN();
// NOCOMMIT -- 64b
out += "(" + cvtToStr(dtypep->widthMin()) + ", " + "__VscopeHash, "
+ std::to_string(salt) + "ull);\n";
}
Expand All @@ -816,7 +808,6 @@ string EmitCFunc::emitVarResetRecurse(const AstVar* varp, bool constructing,

void EmitCFunc::emitVarResetScopeHash() {
if (m_createdScopeHash) { return; }
// NOCOMMIT -- name?
if (m_class) {
puts("uint64_t __VscopeHash = " + std::to_string(std::hash<std::string>{}(m_class->name()))
+ "ULL;\n");
Expand Down
0